Expert consensus holds that a deficit in response inhibition is a core feature of ADHD (Barkley, 1998). Supporting this, neuropsychological research suggests that ADHD persons' commonly perform poorly on tasks that require inhibition of response. These tasks, called Go/No-Go or Stop Signal tasks, require continual manual responding to successively presented stimuli and an occasionally withheld response following a predefined signal. Numerous neuropsychological studies have shown that ADHD children, teens, and adults respond more variably on Go trials on such tasks. They also have longer reaction times and more failures to inhibit responses on No-Go trials (Koshack et al., 2003; Oosterlaan, et al., 1998; Wodushek & Neumann, 1999). Psychostimulant medications like methylphenidate improve performance deficits (Bedard et al., 2003).